Arc lamp



April 20, 1948. R. E. SHEAHAN ARC LAMP Filed Sept. 25, 1946 Inventor:

Robert E. Sheahan b mmyw His Ac.oT-T1eg- Patented Apr. 20, 1948 ARCLAlVIP Robert E. Sheahan, Bridgeport, Conn, assignor to General ElectricCompany, a corporation of New York Application September 25, 1946,Serial No. 699,287

2 Claims. 1

My invention relates to are lamps, and more particularly to electrodefeed control systems for such lamps.

The invention has for its principal object the provision of a new andimproved apparatus for continuously feeding and simultaneously rotatingan arcing electrode.

A further object of the invention is to provide, in conjunction withsuch apparatus, an electrode feeding and rotating mechanism which shallbe of simple, light, and inexpensive construction without sacrifice ofdurability and dependability in operation.

In the operation of arc lamps, such as searchlights and the like, it hasheretofore been common to continuously rotate but only intermittentlyadvance the positive electrode. Purely intermittent advancement of thepositive electrode may be disadvantageous in that it causes considerablefluctuation of the arc. Alternatively, it has been suggested that thepositive electrode may be continuously rotated and continuously advancedat a predetermined constant speed. Such an arrangemnt, however isdifficult to adjust, and if not adjusted for precisely the proper rateof feed the crater will not remain in the desired position.

According to my invention the positive electrode of an arc lamp iscontinuously rotated and continuously advanced at one of two selectablespeeds. The low speed of advancement is slightly less than and the highspeed slightly greater than the normal burning rate of the electrode. Inthis way, the advantages of continuous forward feed and rotation areobtained, but means are also provided to ensure that the crater remainsin the desired position in the event that the burning rate variesslightly.

For a more complete understanding of my in vention and a furtherappreciation of its objects and advantages, reference should now be hadto the following detailed specification, taken in conjunction with theaccompanying drawing, the single figure of which is a schematic circuitdiagram of an electrode feed control system for are lamps embodying myinvention, the electrode feed mechanism being shown in cross section.

Referring now to the drawing, I have shown an arc Searchlight comprisinga positive electrode and a negative electrode 2 arranged to be connectedthrough a contact 3 of a line contactor 4 to the corresponding terminalsof a suitable source high voltage electric current supply, such as a60-volt direct current generator 5. The line contactor 4 is providedwith an actuating wind- 2 ing 6 arranged to be energized through cut-outswitch 1 from a low voltage source of control power, such as a 24-voltline 8.

The negative electrode 2 is supported by a pair of driving rollers Hi,i5 and a pair of spring pressed electric conducting guide brushes It,ll. Current is supplied to the electrode 2 through the brushes l6, IT,as shown. The roller i5 is serrated and driven by a reversible negativedrive motor l8, thereby to advance or retract the electrode 2. The drivemotor i8 is provided with a normally engaged magnetic brake i9 and apair of oppositely wound series field windings 26, 2|. The magneticbrake i9 is arranged to be disengaged upon energization of the motor 8by a brake coil 22 connected in series circuit relation in the motorcircuit. The series field windings 20 and 2| are arranged to bealternatively connected to the source or control power 3 through theswitch 1 and a current regulator 23. The regulator 23 comprises acurrent responsive actuating winding 26, a pair of normally closedcontacts 25 and a pair of normally opened contacts 26. The winding 2 isconnected in series circuit relation in the arc circuit of theelectrodes and 2. The contacts 25 and 26 are controlled by bridgingcontact 27. The motor 18, when energized through the series fieldwinding 2!, is arranged to drive the electrode 2 in a forward directiontoward the electrode i. The motor field winding 26, when energized,causes the motor I3 to operate in the opposite direction, thereby toretract the electrode 2. The field winding 25) is energized through thecontacts 25 only when the current through the arc, and thus through theregulator winding 24, exceeds a predetermined maximum value.

The positive electrode i is arranged for continuous rotation and forwardfeed alternatively at one or the other of two selectable speeds. Forthis purpose the electrode is mounted in a rotatable head 28 which isjournaled in a fixed support 29. The head 28 comprises a hollow sleeve30 within which the electrode is slidable loosely. The sleeve 3%)carries at one end a gear bracket 3i. In the gear bracket 3| theelectrode is supported between a guide roller 32 and a serrated ortoothed driving roller 33. The electrode is further guided and alsosupplied with current by a pair of spring-pressed electric conductingsliders 34 and 35. Upon the shaft of the driving roller 33 there ismounted a driving pinion 36. The pinion 35 meshes with a worm gear 31journaled at 33 in the rotatable head bracket 3|. The shaft of the wormgear 37 carrles at its opposite end a planetary spur gear 39 whichmeshes with a sun gear 48 journaled in the frame 29 and rotatable withrespect to the electrode head 28. Specifically the sun gear 40 isattached to a hollow sleeve 4| which is journaled in the frame 29. Onthe sleeve 4| adjacent to the sun gear 40 there is mounted a spur gear42. The hollow sleeve 39 forming part of the rotatable head 23 isrotatably journaled within the sleeve 4|. At the end of the sleeve 30remote from the gear bracket 3| there is mounted a spur gear 43 fixed tothe sleeve 30 by a setscrew 44. The spur gear 43 is of slightly greaterdiameter than the spur gear 42'. Finally the gears 42 and 43 aresimultaneously and continuously driven by a pair of pinions 45 and 46.The pinions 45 and 46 are journal'ed in the frame 28 and connected, asby a shaft 41 (indicated schematically), to a driving motor 48. Thepinion 46 is slightly smaller than the pinion 45, so that the spur gear42 is driven at a greater speed than the gear 43. It will of course beappreciated that, if desired, the gear 42 may be driven slightly slowerthan the gear 43, it being only necessary that the gears 42 and 43 bedriven at unequal speed. It may be noted however that if the speedrelationship is reversed from that shown it is also necessary to reversethe dlrection of rotation of the motor 4% so that the electrode I willadvance.

It will be observed that, in the operation of the positive electrodedriving mechanism, the spur gear 133, driven by the motor 48 andattached to the electrode head 28, rotates the electrode head about its"own axis, thereby continuously to rotate the electrode I. If now thespur gear 42' were not driven, but were allowed to rotate idly upon thesleeve 36, it would be carried around by the supporting head '28 and thegears 3"! and 39 at the same speed as the head, so that the gears 3'!and 39 would not Totate upon their own axis and therefore would notdrive the electrode 1 longitudinally. However, the spur gear 4'2 ispositively driven by the pinion 45 at a speed slightly greater than thespeed of the head 28 itself. Thus the planetary gear to is caused toroll slowly around the sun gear to, thereby to rotate the worm gear 31on its own axis and continuously to drive the positive electrode Iforward as 'it rotates.

As will be more fully explained hereinafter, the crater at the end ofthe positive electrode 1 is maintained in a predetermined desired.position by providing two selectable driving speeds for the positivehead mechanism, in conjunction with a control system responsive tocrater position. During normal arcing operation the positive drivingmotor .8 is connected to the low voltage source of control power '8through the cut-out switch 1. The motor 48 is provided with a shuntfield winding '48. For control of the speed of the motor 48 there isconnected in series with the motor armature a variable resistor -59which arranged to be shunted by a thermally responsive switch 51. Theswitch 51 is closed when cold and opens its contacts when hot to insertthe resistor to in the motor circuit.

The thermally responsive switch '51, and thus the speed of the motor4-3, is controlled in accordance with the position of the crater in theend or the positive electrode I. Tlns'control may conveniently beeffected by any well known optical system such as that described in U.Patent 1,590,543 issued on June 29, I926, to Martin L. Patterson.Briefly such a system comprises an optical arrangement for reflectingthe image of the positive crater directly upon the thermal responsiveswitch member 5| when the crater is in the desired position. In thisposition of the crater the switch 5! is held open and the motor 48operates at its low speed. If however the crater burns back farther thandesired the image of the crater moves on of the thermal responsiveswitch member 5!. The switch 5| closes its contacts and the speed of themotor 43 is increased, thereby to drive the electrode I forward at. agreater speed.

With the foregoing description of the various elements of my feedcontrol system, the operation of the system as a whole will now bereadily understood from the following brief description.

Let it be assumed that the electrodes are separated as illustrated, andthat the cut-out switch I is closed. With the cut-out switch I closed,energizing circuits are completed for the driving motors i8 and t8, thecircuit for the negative drive motor 58 passing through the bridgingcontact 2? of the regulating relay 23. In parallei circuit relation withthe motors there is also completed an energizatlon circuit for theactuating Winding 5 of the line contactor 4. Accordingly, therefore, assoon as the switch "I is closed the drivin motors l3 and '48 are placedin operation and the line contactor 4 is picked up to apply arcingvoltage to the electrodes.

Since no are yet exists, the regulator contacts 25 are closed and thenegative driving motor drives the electrode 2 forward into engagementwith the electrode The positive electrode l is simultaneously beingdriven forward at its maximum speed because the thermal responsiveswitch member 5i is cold and the resistor 50 shunted. As soon as theelectrodes come into contact an arc is struck. The high current throughthis short are picks up the regulating relay '23, thereby to close thecontacts 26 and to withdraw the electrode 2 by reverse operation of themotor is. With arcing taking place, the crater at the end of thepositive electrode l is maintained in a predetermined desired positionby operation of t e thermal responsive member 55 and the motor :33, andthe negative electrode is advanced or retracted as required in order tomaintain the arc current substantially constant.

While I have described only a preferred embodiment of my invention byway of illustration, modifications will occur to those skilled in "theart, and I therefore wish to have it understood that I intend in theappended claims to cover all such modifications as fall within the truespirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In an arc lamp including a pair of arcing electrodes, electrode feedcontrol means for continuously rotating and advancing at least one ofsaid electrodes comprising, a rotatable electrode holder, a concentricsun gear rotatable with respect to said holder, a planetary gearjournaled in said holder meshing engagement with said sun gear, andmeans for continuously and positively driving said holder and said sungear at unequal speeds.

2. In an arc lamp including a pair of arcing electrodes, electrode feedcontrol means for con tinuously rotating and advancing at least one ofsaid electrodes comprising, a rotatable electrode holder, a concentricsun gear rotatable with respect 'to said holder. a planetary gear.journaled in said holder in meshing engagement with said sun gear,means actuated by rotation of said planetary gear about its own axis foradvancing said electrode, and means for continuously and positivelydriving said holder and said sun gear at unequal speeds.

ROBERT E. SHEAHAN.

REFERENCES CITED file of this patent:

Number UNITED STATES PATENTS Name Date Thompson June 8, 1926 Mole Oct.12, 1926 Pennow Dec. 13, 1938

